生长曲线参数估计的一种新方法-优化回归组合法

在现有文献研究的基础上,对生长曲线参数估计问题又作了进一步研究,给出了生长曲线参数估计的一种新方法优化回归组合法,该方法创造性地将最优化方法与回归方法结合在一起,利用最优化理论中的区间搜索和一维搜索,可以得到一系列c^＊值,利用回归方法可求得与其相对应的一系列a和b的值．当c取最优值c时,a和b便得到最优值a^＊和b^＊经示例计算表明,这种参数估计法具有较高的精度,     

Gompertz生长曲线模型参数的伴随同化估计

利用伴随同化方法研究了Gompertz生长曲线模型参数估计问题.以1790-2000年美国人口数据为例进行了数值实验,实验结果显示该方法是可行的.     

不同日粮蛋白水平对昆明小鼠仔鼠断奶前生长发育的影响

分别给5组昆明小鼠雌鼠14%、16%、18%、20%和22%蛋白水平的日粮后配种。测定其产仔数、仔鼠初生重,每隔两日称重至3周龄断奶,然后采用生长曲线方程拟合生长曲线。根据所获得的参数计算相对生长率,拟合相对生长曲线。结果表明:Gompertz 方程能够很好地拟合仔鼠断奶前的生长发育过程。通过分析蛋白水平对参数估计值、累积生长曲线、相对生长率、相对生长曲线的影响,表明14%蛋白水平显著影响仔鼠的生长发育,妊娠和哺乳期昆明小鼠的蛋白质需要为18%。     

用麦夸方法最优拟合逻辑斯谛曲线

一般对非线性逻辑斯谛生长曲线的拟合是采用首先对原方程线性化以后用线性最小二乘的方法。此方法不是最优的。本文提出用麦夸方法对曲线进行拟合,并且比较了Gause、Andrewartha、May、Pearl、Krebs、万昌秀等人提出的方法与计算结果。麦夸方法对生物实验及生态学中诸多非线性曲线的参数估计具有普遍的意义。     

运用遗传算法拟合Logistic曲线的研究

Logistic方程是研究有限空间内种群增长规律的重要工具之一．本文运用遗传算法拟合logistic曲线,并且比较了各种方法的拟合结果,证明遗传算法具有较强的拟合非线性方程的能力,对生物实验及生态、生理学中诸多非线性曲线的参数估计具有普遍意义．     

蛋黄液中沙门氏菌温度预测模型的建立

为探究温度对沙门氏菌在蛋液中生长规律的影响,测定了在4、10、15、20、25、30、37和42℃等不同温度下沙门氏菌的生长曲线,利用Origin 8.0软件中非线性最小二乘法的原理进行修正Gompertz方程、修正Logistic方程的拟合以及DMFit软件进行Baranyi模型的拟合,研究结果表明修正Gompertz模型、修正Logistic模型和Baranyi模型均能得到较高的决定系数(0.99),选取决定系数相对较高的修正Logistic模型进行一级模型的建立。通过参数估计后利用Ratkowsky模型对最大比生长速率以及迟滞期进行二级模型的拟合,通过Baranyi模型得到的生长参数建立的二级模型拟合度高于其他模型,最大比生长速率以及迟滞期二级模型决定系数分别为0.978和0.866。经检验,研究建立的模型可用于10~42℃温度范围内蛋黄液中沙门氏菌的生长预测。     

基于遗传算法的羊肚菌液体发酵动力学模型的建立

发酵动力学研究是实现发酵过程最优化控制及发酵过程放大的前提条件。本研究对羊肚菌液体深层发酵动力学进行了研究, 在Matlab软件平台上, 应用遗传算法对比了真菌生长较常用的Monod与Logistic方程在描述羊肚菌生长动力学时的优劣, 并对羊肚菌的生长、胞外多糖产生和基质消耗模型进行了参数估计。结果表明, Logistic方程与试验数据拟和情况更好, 并给出了羊肚菌液体深层发酵的动力学模型具体形式, 经验证, 模型的平均误差为5.8%。利用遗传算法选择羊肚菌动力学模型, 并进行参数估计与其他方法相比具有快速、搜索面广、接近全局最优解的特点, 在处理分批发酵动力学问题上具有不可比拟的优势, 发酵动力学模型的建立为发酵过程优化及放大奠定了基础。     

运用改进单纯形法拟合Logistic曲线的研究

Ｌｏｇｉｓｔｉｃ方程是研究有限空间内种群增长规律的重要工具之一本文运用改进单纯形法最优拟合Ｌｏｇｉｓｔｉｃ曲线,结果表明改进单纯形法具有较强的拟合非线性方程的能力,对生物实验及生态、生理学中诸多非线性曲线的参数估计具有普遍意义．     

一种获得非线性生长函数参数初始值的新方法:杂种遗传算法

本研究旨在杂种遗传算法应用于非线性生长函数的参数估计.提出了杂种遗传算法估计非线性生长函数参数的数学模型.5种非线性生长函数Gompertz、Logistic、von Bertalanffy、Richards、Brody分别拟合一个较大型的、群体类型差异大的番鸭体重生长资料,利用杂种遗传算法获得了有效初始值,在lsqcurvefit与proc nlin中获得了一致最优解的结果.表明杂种遗传算法估计非线性函数参数的实际可行性.     

利用差异演化算法优化土壤特征曲线参数

差异演化法是一种在连续空间全局最优化问题上简单有效的新型智能进化算法.利用非饱和土壤数据库UNSODA的不同数据集和差异演化算法预测土壤特征曲线参数,获得对不同环境(田间、实验室)和土壤湿度(湿润、干燥)的参数估计,以及土壤质地、样本的选取对参数估计和拟合精度的影响.结果表明:基于实验室中测得的干土壤数据的参数估计和特征值具有最高精度;在四种不同质地的土壤中,黏土的均方根误差最小,土壤特征曲线的拟合精度较好,饱和含水量和残余含水量都较高,砂土的相应参数估计精度则较低;样本容量对于参数的拟合均值影响较小.     

Recent advances in the study of Kaposi's sarcoma-associated herpesvirus replication and pathogenesis

It has now been over twenty years since a novel herpesviral genome was identified in Kaposi's sarcoma biopsies. Since then, the cumulative research effort by molecular biologists, virologists, clinicians, and epidemiologists alike has led to the extensive characterization of this tumor virus, Kaposi's sarcoma-associated herpesvirus(KSHV; also known as human herpesvirus 8(HHV-8)), and its associated diseases. Here we review the current knowledge of KSHV biology and pathogenesis, with a particular emphasis on new and exciting advances in the field of epigenetics. We also discuss the development and practicality of various cell culture and animal model systems to study KSHV replication and pathogenesis.     

A Unique Protease Cleavage Site Predicted in the Spike Protein of the Novel Pneumonia Coronavirus (2019-nCoV) Potentially Related to Viral Transmissibility

正Dear Editor,In December 2019, a novel human coronavirus caused an epidemic of severe pneumonia(Coronavirus Disease 2019,COVID-19) in Wuhan, Hubei, China(Wu et al. 2020; Zhu et al. 2020). So far, this virus has spread to all areas of China and even to other countries. The epidemic has caused 67,102 confirmed infections with 1526 fatal cases     

Curcuminoids as inhibitors of thioredoxin reductase: A receptor based pharmacophore study with distance mapping of the active site

Curcumin is the yellow pigment of turmeric that interacts irreversibly forming an adduct with thioredoxin reductase (TrxR), an enzyme responsible for redox control of cell and defence against oxidative stress. Docking at both the active sites of TrxR was performed to compare the potency of three naturally occurring curcuminoids, namely curcumin, demethoxy curcumin and bis-demethoxy curcumin. Results show that active sites of TrxR occur at the junction of E and F chains. Volume and area of both cavities is predicted. It has been concluded by distance mapping of the most active conformations that Se atom of catalytic residue SeCYS498, is at a distance of 3.56 from C13 of demethoxy curcumin at the E chain active site, whereas C13 carbon atom forms adduct with Se atom of SeCys 498. We report that at least one methoxy group in curcuminoids is necessary for interation with catalytic residues of thioredoxin. Pharmacophore of both active sites of the TrxR receptor for curcumin and demethoxy curcumin molecules has been drawn and proposed for design and synthesis of most probable potent antiproliferative synthetic drugs.     

The structure, reproduction and taxonomy of Vidalia and Osmundaria (Rhodophyta, Rhodomelaceae)

Comprises species occurring mostly in subtidal habitats in tropical, subtropical and warm-temperate areas of the world. An analysis of the type species, V. spiralis (Sonder) Lamouroux ex J. Agardh, a species from Australia, establishes basic characters for distinguishing species in the genus. These characters are (1) branching patterns of thalli, (2) flat blades that may be spiralled on their axis, (3) width of the blade, (4) primary or secondary derivation of sterile and fertile branchlets and (5) position of sterile and fertile branchlets on the thalli. Application of the latter two characters provides an important basic method for separation of species into three major groups. Osmundaria , a genus known only in southern Australia, was studied in relation to Vidalia , and its separation from the Vidalia assemblage is not accepted. Species of Vidalia therefore are transferred to the older genus name, Osmundaria. Two new species, Osmundaria papenfussii and Osmundaria oliveae are described from Natal. Confusion in the usage of the epithet, Vidalia fimbriala Brown ex Turner has been clarified, and Vidalia gregaria Falkenberg, described as an epiphyte on Osmundaria pro/ifera Lamouroux, is revealed to be young branches of the host, Osmundaria prolifera.     

New or rare chromosome counts in Artemisia L. (Asteraceae, Anthemideae) and related genera from Kazakhstan

Fifteen chromosome counts of six Artemisia taxa and one species of each of the genera Brachanthemum, Hippolytia, Kaschgaria, Lepidolopsis and Turaniphytum are reported from Kazakhstan. Three of them are new reports, two are not consistent with previous counts and the remainder are confirmations of very scarce (one to four) earlier records. All the populations studied have the same basic chromosome number, x = 9, with ploidy levels ranging from 2x to 6x. Some correlations between ploidy level, morphological characters and distribution are noted.